This invention relates to a process for producing a solid foaming agent body and to a process of using said body for the removal of water from a gas well borehole by foam generation.
When a gas well is flooded, a column of water forms in the borehole which reduces the flow of the gas from the well. Several methods exist to remove the water from the borehole. For example, the water may be pumped to the surface; however, this is both time and energy consuming. Liquid foaming agents are available which may be pumped to the bottom of the column of water to attain efficient foam generation, but they involve the expense of servicing the well. A preferred alternative is to drop a solid foaming agent down the borehole. As the solid dissolves, gas from the producing zone passing through the column of water generates foam which allows the water to be blown out of the well.
In principle, any water soluable surface active agent with foaming capabilities could be used to remove water from boreholes by foam generation. However, when it is desirable to use a solid foaming agent, certain classes of surfactants are preferred. In particular, some members of the class of polyethyoxylated nonionic surfactants, being hard waxes at ambient temperatures, can be readily melted and cast into molds for use as solid foaming agents. Inorganic salts may be added to increase the bulk density of such compositions. An example of this type of foaming agent is disclosed in U.S. Pat. No. 3,251,417 to Holman et al.
These solid foaming agents are usually molded into long cylindrical sticks approximately 3 cm in diameter and 30 to 50 cm in length. During warm weather these products tend to become soft and waxy and are difficult to drop down the well borehole.
A more serious problem of these prior art compositions is their low rate of solubility. In order to generate foam in a reasonably short period of time an excessive quantity of the solid foaming agent is added to the well. Even in large amounts, these foaming agents often take in the order of 3 to 4 hours to expel water from the well. After most of the water has blown out of the well, the foaming agent continues to slowly dissolve in the residual water. The foam thus generated becomes incorporated in the gas production, which is undesirable.
It is known in the field of surfactant chemistry to combine liquid surfactants or detergents with urea to form solid urea adducts. The adducts decompose in water to release urea and the uncomplexed surfactant. It has generally been found that urea adducts can be formed with many straight chained hydrocarbons, fatty acids and alcohols, whereas highly branched hydrocarbons remain substantially uncombined with urea. Urea forms a helical structure in which the surfactant is trapped or held. Apparently straight chain hydrocarbons, or those with a low degree of branching or ring formation can more easily fit into the helical structure and thus form the urea adducts.
To our knowledge no one has yet attempted to utilize these urea adducts in the removal of water from well boreholes.